Problem: What's the first wrong statement in the proof below that $ \triangle CEB \cong \triangle CAB$ $ \; ?$ $ \overline{BC} $ is parallel to $ \overline{DF} $. This diagram is not drawn to scale. $A$ $B$ $C$ $D$ $E$ $F$ Givens $ \overline{AC} \cong \overline{DE}$ $, \ $ $ \angle ACB \cong \angle BDE$ $, \ $ $ \overline{BC} \cong \overline{BD}$ $, \ $ $ \overline{AB} \cong \overline{EF}$ $, \ $ $ \angle BAC \cong \angle CEF$ $, \ $ and $\ $ $ \angle ACB \cong \angle ECF$ Proof $ \triangle DEB \cong \triangle CAB$ because SAS $ \overline{BE} \cong \overline{AB}$ because corresponding parts of congruent triangles are congruent $ \angle BEC \cong \angle BED$ because corresponding parts of congruent triangles are congruent $ \triangle CAB \cong \triangle CEF$ because AAS $ \angle BED \cong \angle BAC$ because corresponding parts of congruent triangles are congruent $ \triangle CEB \cong \triangle CAB$ because SSS
Try going through the proof yourself: write down the givens, and then see if they justify the next step for the reason given. Then do the same thing for the next step, and the next, until you run into something that you can't justify, or you finish the proof. $ \angle BED \cong \angle BEC$ is the first wrong statement.